I propose to use cell culture techniques to investigate the control of differentiated functions in pretumorous lesions of mouse mammary glands. Comparisons with normal and tumor cells will be made. I must first optimize conditions for maintaining normal, preneoplastic, and neoplastic epithelial cells in culture. It is anticipated that there will be differences in the growth responses (DNA and protein accumulation) of these cells to culture-medium composition (serum and hormones especially). Having learned how to grow these cells, I will then establish assays for the differentiated secretory products (milk and virus) of mammary epithelia. I will then determine the influence of medium components (hormones in particular) and other cell types (fibroblasts) on these syntheses. I will investigage the relationship between differentiated syntheses and multicellular organization, and will compare patterns of mild and virus controls by hormones. It will eventually be possible to begin to explore in detail the controls on protein synthesis in the hyperplastic alveolar nodule cells (and how these controls compare with those in normal and neoplastic cells). I will concentrate on translation-level controls, using defined messenger RNAs and supernatant components from the 3 cell types in the heterologous cell-free systems.